title: Accuracy of acetabular component position in hip arthroplasty.
abstract: BACKGROUND
  Acetabular component malposition is linked to higher bearing surface wear and component instability. Outcomes following total hip arthroplasty and surface replacement arthroplasty depend on multiple surgeon and patient-dependent factors. The purpose of this study was to examine the frequency in which acetabular components are placed within a predetermined target range.
  
  
  METHODS
  We evaluated postoperative anteroposterior pelvic radiographs for every consecutive primary total hip arthroplasty and surface replacement arthroplasty completed from 2004 to 2009 at a single institution. Acetabular component abduction and anteversion angles were determined using Martell Hip Analysis Suite software. We defined target ranges for abduction and anteversion for both total hip arthroplasty (30° to 55° and 5° to 35°, respectively) and surface replacement arthroplasty (30° to 50° and 5° to 25°, respectively). Surgeon and patient-related factors were analyzed for risk associated with placing the acetabular component outside the target range.
  
  
  RESULTS
  Of the 1549 total hip arthroplasties, 1435 components (93%) met our abduction target, 1472 (95%) met our anteversion target, and 1363 (88%) simultaneously met both targets. Of the 263 surface replacement arthroplasties, 233 components (89%) met our abduction target, 247 (94%) met our anteversion target, and 220 (84%) simultaneously met both targets. When previously published target ranges of abduction (30° to 45°) and anteversion (5° to 25°) angles were used, only 665 total hip replacements (43%) met the abduction target, 1325 (86%) met the anteversion target, and 584 (38%) simultaneously met both targets. Of the surface replacement arthroplasties, 181 (69%) met the abduction target, 247 (94%) met the anteversion target, and 172 (65%) simultaneously met both targets. Low-volume surgeons were 2.16 times more likely to miss target component position compared with high-volume surgeons (p = 0.002). The odds of missing the target increased by ≥ 0.2 for every 5 kg/m2 increase in body mass index. Minimally invasive approaches, diagnosis, years of surgical experience, femoral head size, and age of the patient did not affect component position.
  
  
  CONCLUSIONS
  Increased odds of component malposition were found with lower-volume surgeons and higher body mass index. No other variables had a significant effect on component placement.
  
  
  METHODS
  Therapeutic Level III. See Instructions for Authors for a complete description of levels of evidence.
authors.affiliation: Department of Orthopaedic Surgery, Washington University School of Medicine, 660 South Euclid Avenue, Campus Box 8233, St. Louis, MO 63110. E-mail address for R.L. Barrack: barrackr@wustl.edu.
authors.forename: Robert L
authors.initials: RL
authors.lastname: Barrack
authors.forename: Jeffrey A
authors.initials: JA
authors.lastname: Krempec
authors.forename: John C
authors.initials: JC
authors.lastname: Clohisy
authors.forename: Douglas J
authors.initials: DJ
authors.lastname: McDonald
authors.forename: William M
authors.initials: WM
authors.lastname: Ricci
authors.forename: Erin L
authors.initials: EL
authors.lastname: Ruh
authors.forename: Ryan M
authors.initials: RM
authors.lastname: Nunley
mesh_terms: D000077:Acetabulum / Q000601:surgery*; D019644:Arthroplasty, Replacement, Hip / Q000379:methods / Q000592:standards*; D017760:Bone Malalignment / Q000517:prevention & control; D002983:Clinical Competence / Q000592:standards; D006622:Hip Prosthesis / Q000592:standards*; D006801:Humans; D009985:Orthopedics / Q000592:standards; D011446:Prospective Studies